mercury_editor-2.0.x-dev/build/js/node-form.js

(function () {
  'use strict';

  ((Drupal, once) => {
    Drupal.behaviors.mercuryEditorNodeForm = {
      attach: function(context, _settings) {
        if (!once('me-entity-form', '.me-entity-form', context)) {
          return;
        }
        // Add a class to the form if an input, textarea, or select is changed.
        document.querySelector('form.me-entity-form').addEventListener('change', (e) => {
          e.target.closest('form').classList.add('unsaved-changes');
        });
        // Warn the user if attempting to leave the page with unsaved changes.
        window.addEventListener('beforeunload', (e) => {
          if (document.querySelector('.me-entity-form.unsaved-changes')) {
            e.preventDefault();
            e.returnValue = '';
          }
        });
      }
    };
  })(Drupal, once);

})();